Telephone-exchange system



' E. H. CLARK TELEPHONE EXCHANGE SYSTEM Jan. 29, 1929.

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1,700,467 E. H. CLARK TELEPHONE EXCHANGE SYSTEM Filed Aug. 4, 1927 9 Sheets-Sheet 2 .Illlll In [2764/7 f7. CLARK By W Arron/wry Jan. 29, 1929. 1,700,467

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Filed Aug. 4, 1927 9 Sheets-Sheet 4 AWE/v al? [004R /7. 62AM 15V Arron/v5) Jan. 29; 1929.

E. H. CLARK TELEPHONE EXCHANGE SYSTEM Filed Aug. 4, 1927 9 Sheets-Sheet 5 fivvlwran [06 417 /7. 62AM By W W Arronmsv Jan. 29, 1929.

E. H. CLARK TELEPHONE EXCHANGE SYSTEM 9 Sheets-Sheet 6 Filed Aug. 4, 1927 Jan. 29, 1929; 1,700,467

" E. H. CLARK TELEPHONE EXCHANGE SYSTEM Filed Aug. 4, 1927 9 Sheets-Sheet 7 ATTORNEY Jan. 29, 1929.

1,700,467 E. H. CLARK TELEPHONE EXCHANGE SYSTEM Filed Aug. 4, 1927 9 Sheets-Sheet 8 /A/VEN7'0/? [00,45 /7f 62AM BVWW Jan. 29, 1929.

E. H. CLARK TELEPHONE EXCHANGE SYSTEM 9 Sheet-Sheet 9 Filed Aug. 4, 1927 /NVNTOR EDGAR hf CLARK 5) WV ATTORNEY Patented Jan. 29, 1929.

urrso STATES PATENT OFFICE.

EDGAR H. CLARK, OF RICHMOND HILL, NEW YORK, ASSIGNOR TO BELL TELEPHONE LABORATORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed August 4, 1927. Serial No. 210,516.

This invention relates to telephone ex change systems and its object is to improve the control and operation of automatic switches.

According to a feature of the invention, a master control circuit normally serves to control a plurality of line switches and a second master circuit normally controls an other plurality of line switches to extend calling lines, either control circuit, however, being capable under certain conditions of controlling all said line switches.

Another feature of the invention is a master circuit having group and individual relays for determining which of a plurality of subscribers line is to receive attention when calling, other calling lines being delayed temporarily. 7

According to a further feature, a plurality of trunks, arranged in groups and Inultipled before a number of line switches, are tested, a plurality of groups at a time, until an idle trunk is found. 7

According to a further feature, the line relays do not start a master circuit in operation unless they are in condition to exercise full control over such master circuit by also operating certain other relays in the master circuit. y

, Referring to the drawing, Figs. 1 to 9 inclusive when arranged in the order shown in Fig. 10, disclose the details of a system embodying the invention.

Fig. 1 shows a number of subscribers lines together with certain controlling apparatus.

Fig. 2 shows one of a number of coordinate line switches in which the subscribers lines terminate.

Fig. 3 shows a portion of two master controlling circuits.

Fig. 4 illustrates the connectors for connecting the master circuits to the line switch frames.

Figs. 5 and 6 show portions of the two master circuits.

Fi 7 illustrates connectors for connecting he master controlling circuits to the line itchesa s Fig. 8 shows the group and units relays in one of the master ClICUlbS for determining the group of calling lines to receiveattent1on.

master controllingcircuit.

of the other master circuit.

Fig. 9 shows similar relays for thesecond of a master control circuit normally controlling each of two line switches and a second master controllingcircuit for a second pair of line switches. The subscribers lines are distributed among the four line switch frames of the two pairs, no line appearing in more than one line switch. The trunks outgoing from the four line'switches comprise a single group, each trunk appearing in each of the four switches.

Normally, each master circuit controls its pair of line switches to extend the calling lines to the group of trunks independently Certain provisions are made whereby interference is prevented when both master circuits are attemptingsimultaneously to extend calls. In the case of troublein one of the master circuits, or if for any reason a master. circuit is disabled or taken out of'service, the circuits are so arranged that the other master controlling mechanism can control all four of the line switches.

Referring to Fig. 2, the calling subscribers lines appear in the line switch 200 and similarly in the other switches (not shown) in vertical rows of contacts. The Vertical rows 201, 202, etc., are illustrated. The trunks outgoing from the line switch also appear in vertical rows 203, 204, 205, 206, etc. Each switch is divided into a number of horizontal groups of which two groups 207 and 208 are illustrated. The group 207 includes a plurality of horizontal links 209, 210, etc. Likewise, the group 208 includes a number of links 211, 212, etc. It willbe noted that the subscribers lines 100 and 101 each appear before the links of a single horizontal group. Each of the trunks 221 to 228 appears before one horizontal link in each of the horizontal groups.

The multi-contact relay 305 shown in Fig. 3 serves to connect the individual line circuits through to the horizontal group relays 307, 308, etc., in the master circuit which normally controls the pair of switches including the switch 200. The' relay 306 is used in case of emergency to connect the in-,

dividual line circuits appearing in the other to the other pair of liralnes.

Figs. 5 and (3 show the tes ing equipment for both inaster control-circnits. In order to test agroup of trunks, there is provided a series of testrelays in-er :1]. master circuit. lhese relays are applied tothe trunks in such a manner-that all of the trunks'ina pair of vertical rows are si nultaneously tested. If they are all "busy-the testrelays are disconnected and iinn'iediately reconnected to test in the next pair of vertical rows. This proce dure is continued until an idle trunk is found, which at the same time may 'be reached througlran idle horizontal link. For example, the testrelays may first he applied to the trunks appearing inthe two vertical rows 205 and 206 of the line switch 200. 'ltthe calling line is in the horizontal group 207, then the -=test will beconlined to the trunks appearing in this-horizontal group. There ill be a number of pairs of such trunks however. For instance, the trunks 2 7 and 225 may comprise the odd andeven trunks, respectively, of the pairappearing before the horizontal link 209. T he trunlzs228 and 226 comprise the odd and even trunks, respectively, of the next pair appearing beiore the-link 210. Similarly, there will he as many pairs of trunks as there are horizontal-links in the group 207,. Inthe master control circuit noianally serving the switch 200 ther .ys 612an'd 517 are the odd and cventes' s, respectively. The relay no trunk 21, and the relay "The relay 510 which is associated with the relays 517 and (512 serves to test the corrcspoin'lin ontinued n1 oair of trunk through the contact oi relay 10%,

'zuided with a series ofitest'relays including the relays 513, 51 i and 609 which are applied through the contacts of relays 506, 507, etc., to the. trunks "in the asso Grated i'rarnes.

Since a celnparatively large uniher oi lines are controlled by a single master c1r- .cuit, it is necessary to nrake seine provision for simultaneous calls. To this end the line 'calrows o t contacts 201, 202, etc, in each pair of switches, are divider into a number of groups. In the control circuit each group is provided with a group relay, such as relays 811, 812, 813, etc. If agroup consists of live vertical rows, then there are provided the units relays 816, 817, etc.,whic'h--are applica hie-to all of-t'he groups. lnxthe case ofs'iinul- 'taneous calls a lur-alit (a yertical groin relays 811, 81 2, rnay be operated; "By means of alocleout circuit however, a preferred one will remain operated and *the'other will re lease. The vertical group relay which remains operated governsthe'operation ofthe corresponding pair of connector relay-s 805, 808, 806, 509, etc. Theo iera ed pair of connector relays associatesthe units relays 816,

817, with the selected group of calling lines and, dependinguponwaicli linein thegroup is calling, the corresponding-one o't' theseuni-ts relays is operated. 'lhe'operated units relay finally detern'iines the operation of the vertical magnet controlling the bar individual to the vertical row containing the selected calling line.

A detailed description of the system will now be given. For this purpose assuniethat the subscriber of line 102' initiates 'a call.

The line relay 10% operates in a circuit from battery through the outer contact oi relay 105, back contact of relay 112, conductor 1 13,

winding of the relay 104C, through 'the contacts of the cut-ofi relay 103 and the subscribers loop to ground. Relay 104 places ground potential on conductor 1'14, causing the operation of the start relay 11 1. relay 111 closes operatingcircuits for relays 305, 400 and -9. These circuits may he traced'frorn battery 'to the winding Ofi' relay 709, conductor 713, back contactof relay 81-9,

conductor 820 and in parallclthwug h the windings of relays 4:00 and 305-to conductor 820, thence throu h the hack contact relay 31S, outer hack of relay $12, conductor 319, to ground at the contact of the start'relay 111. Relay 709 connects the contacts ot the line relays through to the master control'circult. It also connects the vertical group relays 811, 812,818, etc, to the line circuits. clay 709 also operates the relay 815 in a circuit from batt ry through the winding of relay 8'15, conductor 822, contact otrelay 611,'conductor 615, to ground at the contact of relay 709. Since the line 102 is in the group represented by the group relay 812. relay 812 is operated in a circuit from-ground conductor 116, con-tact of relay 709, conductor 715, right winding of relay 812, back contact of relay 819 to battery. Relay 812 locks in a circuit from battery through the outer right contact of relay 814, conductor 821, winding of relay 819 through the armatures and back contacts of all vertical group relays preceding relay 813 through the armature and frontcontact and left-hand winding o1 relay 813 to ground. Relay 819, in operating, releases the relay 709, disconnecting the line relay contacts from themaster circuit. Relay 812 operates the relays 806 and 809 to connect the contacts of the line relays, 01" the group to receive the call, to the mast-er circuit. These relays operate in a circuit from battery to their windings in parallel, contact o'l relay 812, contact of relay 819, conductor 823, to ground at the contact of relay 312.

Relay 817, inoividual to the vertical group 201, is now operated in the circuit from battery through the right back contact of relay 815, right winding of relay 817, uter contact of relay 806, conductor conductor 116, to ground at the Contact 01 104. Relay 815 released upon deenergization of relay 709. Relay 817 locks in a circuit from battery to the winding of relay 815, conductor 822, contact of relay 611, conductor 615, conductor 826, armature and frontcontact and left winding of relay 817 and thence to ground as traced on conductor 116. Relay 815 reoperates in the circuit traced to pre-- vent the subsequent operation of other vertical units relays.

At the time relay 305 operates, a circuit is closed tor the horizontal group relay 307,

traceable from battery through the cont-acts of relays 811 and 310 upper winding of relay 807, contact of relay 305, conductor 320, back contact of relay 110 to the grounded conductor 114. Relay 807 operates and locks in a circuit from battery through the back contacts or" relay 814, conductor 821, winding of relay 311, back contact of relay 808, tront contact and winding of relay 807, conductor 5321, contact oi. relay 400 to the grounded con ductor 114. Relay 307 operates relay 112 in acircuit from battery through the winding of relay 112, conductor 117, contact of relay 400, conductor 407, contact of relay 807, to ground at the contact of relay 811. Belay 112 closes an obvious circuit for relay 110. Relay 110, when operated, opens the en;- gizing circuit of relay 807. Relay 112 closes an obvious circuit for connecting relay 708. Relay 708 connects the master circuit to the line switch 200.

The vertical magnet 213 is now operated to rotate the vertical line bar preparatory to extending the calling line 102 to an idle link circuit. The circuit of magnet 213 may be traced from ground through the winding thereof, conductor 222, contact of relay 708,

conductor 716, conductor 717, contact ot re- -It will next be described how the trunks outgoing from the line switch 200 are tested to determine which vertical magnet is to be operated. For this purpose the first of the connecting relays 501 is energized to associate the test relays with the trunks appearing in the first pair of vertical rows 205 and 206. The circuit for relay 501 may be traced from battery through its winding, back contact of relay 503, conductor 518, through the contact of relay 307 to ground at the contact of relay 311. A circuit is now closed tor slow-operating relay 613 traceable from the grounded conductor 518, through the back contact of relay 503, frontcontact of relay 501, conductor 519, contact of relay 400, conductor 410, contact of relay 108, conductor 120, contact of relay 400, conductor 411, winding of relay 618 to battery. Relay 613 being slow requires an appreciable interval to attract its armatures. This allows su'flicienttime for the test relays to become adjusted.

Relay 612 tests the condition of trunk 227 in a circuit from battery, through the left winding of said relay, outer left "contact of relay 515, conductor 521, contact of relay 501, conductor 522 to the sleeve conductor of the trunk 227. It the trunk is busy relay 612 operates. Relay 517 tests the trunk 225 in a circuit from battery, through the left winding of said relay, and thence over a path similar to that traced to the sleeve conductor of trunk 225. The relay 516 tests the horizontal link 209 before which the trunks 225 and 227 appear. The circuit for this purpose may be traced from battery, through the winding of said relay, contact oi relay 515, conductor 535, contact of relay 400, conductor 412, contact of relay 108 to the test conductor of the link 209. It the link is busy the relay 516 operates and prepares obvious operating circuits for the test relays 517 and 612. Similar circuits are completed from other test relays (not shown) for testing the other trunks appearing in the same horizontal group and in the same two vertical rows. Assuming all the trunks in the rows 205 and 206 are busy, a circuit is completed, as soon as the relay 613 operates, traceable from ground, through the inner left contact of said relay, inner left front grounded conductor 51 8.

contacts of relays 612 and 52? and through front contacts of all similar ope 'ated relays then through the conductor 523, through the- 613 which also releases. As soon as relay 613 releases a cir uit is closed from battery,

through the windiu of relay 500, back contact of relay 502, back contact of relay 613, inner right front contact of relay 503 to the 7 lit will be noted that relay 503 looks through its left winding and contact, thence over conductor 52a to ground it the contact of relay 311. Relay 500 operates and locks in circuit from battery, through its Winding, back contact of relay 502, front contact o'l relay 500, front contact of relay 503 to the grounded conductor 518. Relay 500 associates the test relays, which have been released. by the deen'ergization of relay 501, with the trunks in the next pair of vertical rows 203 and 204-. Slow relay613 also has its circuit reclosed in a path leading; through the front contact of relay 500, tront contact of relay 503 to the grounded conductor 518. This procedure will continue until an idle trunk is found or until all trunks are determined to be busy. If an idle trunk is found in one of the rows 203 or 20 1 a corresponding test relay, such as the relay 517,

remains deenergized.

When the relay. 613 operates following the test which fines an idle trunk, it closes at ri ght contact a circuit tor-holding all operated test relays in their energized condition. At

its left contact it 6" oletes a circuit for the relay 515. This circuit may be traced from ground through the left Contact oi: relay 613, front contact of relay 612, left back contact of relay 51?, to battery, through the winding of relay 515.

The apparatus is now ready to operate the selected vertical magnet on the switch frame. 1? tom the circuit can be traced, however, it will be necessary to describe how one of the vertical relays 50 1, 505 has in the meantime been selected and operated. 'lhese relays individual to a pair of vertical rows on a pair of line switches. At the ti '16 the connector relay 4:00 operates a circuit is closed for the relay 602 traceable from battery, through the winding of said relay, back contact oil. relay 607, conductor 616 to ground at the contact of relay 400. Relay 602 extends the grounded conductor 616 through to the wind g of relay 607. Relay 60? operates and locks to the grounded conductor 52%. At the time relay 515 operates as above explained, a circuit is completed from battery, through the left winding 01 the horizontal operating; magnet- 210, conductor 224:, contact of. relay 108, conductor 112, contact of relay 400, conductor 535, front contact of relay 515, conductor 617, Winding of the marginal relay 605, right high resistance winding of relay 600 to ground. Due to the high resistance of the windingof relay 600, the marginal relay 605 and the horizontal magnet 210 do not operate. Relay 600, however, becomes energ'zed. lhus, with the relay 600 operated and relay 602 energized, as above explained, a circuit is completed tor operating the vertical relay set. This circuit may lie-traced from battery, through the bacl: contact of relay 312, conductor 323, left bacl: contact of relay 608, left winding of relay 50%, back contact of relay 606, front contact of relay 500, conductor 525, front contact of relays 600 and 602, front contact of relay 607, conductor 618 to ground at the back contact of relay 3141-. Belay 504 operates and locks in a circuit from batter through the common lock-out relay 606, contactand right winding of relay 504v and thence to ground as above traced.

The trui'ik vertical magnet 215 is next energized in circuit from ground through its winding, conductor 225, contact of relay 703, conductor 719, front contact of relay 500, conductor 526, outer left contact of relay 612, conductor 620, front contact of relay 504, front contact of relay 603 to battery on the conductor 323.

Magnet 215 in operating closes a circuit from ground, through its lowermost contact, conductor 226, contact of relay 400, conductor winding of relay 603, contact of relay 612, left front contact of relay 515 to the 1 int contact ot relay 500, conductor 113 to the sleeve conductor of t ml: 221 and thence to battery in the selector switch 240. Relay 603 operates and opens the holding circuit of relay 602. Relay 602 releases.

The horizontal magnet 210 is ope-r a circuit from battery, through the left windot said magnet, conductor 22%, contact of r lay 108, conductor 112, contact of relay 400, conductor front contact of relay 515, conductor 6l7, winding of relay 605, conductor 621, contact ot relay 309, conductor 415, back contact of relay 602, contact oi": relay 603 to the grounded conductor 616. The relay 603 which. was operated, as above expla in ated in At the time relay 608 operates it closes an operating 'rcuit for relay 601. Relay 601 operates and closes a circuit from ground, through its right contact, contact of relay 50a, winding of relay 606 to battery. Relay 606 was iiun'iediately shunted down due .ofrelays 504 and 6.08 and these relays release.

magnets 213 and 2.15 are also deenei The connection may be extend d over suce lVhcn the connection is extended through the line switch a circuit is completed from battery, through the winding of the cutol'l relay 103, thence through contacts oi the switch to ground at the first selector 227. Belay 103' releases the line. relay 1042 which removes ground from the holding conductors,

permitting all operated relays in the line switch, and master control circuit to become deenergized. The connection is held from the selector switch which controls the circui of the horizontal magnet 210. Thevertical .acd'.

ceeding switches 241 and 2 12 to, the called subscribers line 243. Then conversation is over the apparatus is released in the usual manner by removing ground potential from the holding conductors in the selectors. The removal of this potential allows the horizontal magnet 219 to release, restoring the line switch 200 to, its normal position.

At the time the runhs are tested if all of them should he found busy a circuit is closed from battery through the winding of the all-trunks-busy relay 611, conductor 622, through contactsfot the operated relays, such as 502-3, 502, etc., to ground. Relay 611 operates an alarm and a peg count register 623.

It may he noted at this point that the line relays, such as relay 104, are equipped with contacts which depend oneonthe other. That is to say unless the first contact is in good condition no circuit is closed through the second contact. This is to prevent starting the n'iasl'er circuit in operation needlessly when the call will fail due to trouble at the other contact of the line relay.

A. description will now be given 01 the opcral '.on when one Ol :19 master control circuits is taken out of service. Assume For this purpose that the master control circuit which normally serves the other pair of "frames (not shown in the drawing) becomes disable-d. Due to the "fact that the master control circuit disabled the relay 318 becomes operated after an interval. in a circuit from battery, through its winding, thence over conductor 325 to ground. The ground potential is applied. by any-suitable timing mechanism not illustrated. lelay 318 trans- .iers the start circuit 326 to conductor 327, thence through the left winding of relay 01.0 to battery, through the contact of relay'815. Relay 316 operates and locks in a circuit f ou'i battery, through the winding of relay 3155, contact and right hand winding of relay 316 to grounded start conductor 326. Relay 315 opens the common operating circuit to prevent the subsequent operation of relay 317. Relay 316 at itsinner left contact places ground on conductor 340 to operate relays" switches hav ng a master control circuit, asecond plurality of switches having a master control circuit, circuits appearing in said switches, each master circuit normally controlling the switches with which it is associated,'and means for rendering one of said master circuits switches assoc atcdwith the other master circu-it I 2. In a telephone system, a plurality of,

swi ches havinga master control circuit, a second plurality of switches having a master c ntrol c cuit, ci cuits ppe r g. in sa d switches, each master circuit normally controlling the switches with which it is aSSociated, and u'icans {or rendering either n. ster circuit eli'ective to control the switches as sociated with the other master circuit.

3. In a telephone system, a plurality of line switches having a master control circuit, a second plurality of line switches having a master control circuit, lines appearing in said switches, each master circuit normally con trolling the switches with which it is associated, and means effective when one master circuit is disabled for rendering the other master circuit etl'cctive to control all of said switches.

41-. In a telephone system, a plurality of line switches having a master control circuit, a second plurality oi line switches having a master control circuit, lines appearing in said switches, each master circuit normally controlling the switches with which it is associated, means responsive to the disabling of either master circuit for rendering the other master circuit effective to control all of said ""1l Gl18S, and means for preventing a master circu it from attempting to control two switches at one time. i

5. In combination, a plurality of switches having a master control circuit, a second plu-' rality ct switches having a master control circuit, lines appearing in said switches, eacheffective to control the control both the switches it normally serves and the switches normally served by the other master circuit.

6. In combination, a plurality of line switches, lines appearing therein in groups, a common master control circuit including a plurality of group relays and a plurality of units relays, and means for operating a group relay and a units relay to determine the group and the line in the group to be extended by one of said switches.

7. In combination, a number of line switches, lines appearing therein in groups and subgroups, a common control circuit including a group relay for each group and a subgroup relay for each subgroup in a group, I

means ior operating a group relay to select a group and a subgroup relay to choose a subgroup therein, and means controlled by the common control'circuit for operating one or" said switches to extend a calling line in the chosen subgroup.

8. In a telephone system, a line switch having rows of contacts, a group of trunks appearing in said rows and divided in subgroups, each sub-group occupying a plurality of said rows, a device for testing the trunks of said group, and means for applying said device to test successively said sub-groups of contacts.

9. In combination, a line switch having rows of contacts, trunks appearing in said rows, a series of relays for malnng a slmul- V taneous test of the trunks in a plurality of rows, and means for connecting said relays in succession, each time to a plurality of rows of trunks.

10. In combination, line switches having rows of contacts, groups of trunks appearing in said rows, each trunk multipled to all switches, a common testing mechanism for making a succession of tests of the trunks, each test applying to the trunks in a plurality of rows, and means for connecting the testing mechanism first to, one group of trunks and then to succeeding groups.

11. In combination, a line switch, lines appearing therein in groups, a common master control circuit including a plurality of group and units relays, line relays, one for each of said lines, a start relay for setting the master circuit in operation to control said line switch, a contact on each line relay for operating the start relay, and a contact on each line relay for operating said group and units relays, said contacts so arranged that the start relay does not operate unless the line relay is in condition to operate said group and units relays.

In witness whereof, I hereunto subscribe my name this 1 day of August A. D., 1927.

EDGAR H. CLARK. 

